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Draft Transportation Conformity Guidance for Quantitative Hot-spot Analyses in PM2.5

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Environmental Protection Agency (EPA).


Notice of Availability; Request for Public Comment.


EPA is announcing the availability of a draft transportation conformity guidance document for public comment. Once finalized, this guidance would help state and local agencies complete quantitative PM2.5 and PM10 hot-spot analyses for project-level transportation conformity determinations of certain highway and transit projects. A hot-spot analysis includes an estimation of project-level emissions, air quality modeling, and a comparison to the relevant national ambient air quality standards (NAAQS) in PM2.5 and PM10 nonattainment and maintenance areas. The U.S. Department of Transportation (DOT) is EPA's federal partner in implementing the transportation conformity regulation, and EPA coordinated with DOT on the development of this draft guidance.


Comments must be received on or before July 19, 2010.


Interested persons may obtain a copy of the draft guidance from EPA's Office of Transportation and Air Quality Web site at:​otaq/​stateresources/​transconf/​olicy.htm

EPA will accept comments as follows:

E-mail: Comments can be sent electronically to the following e-mail address:

Mail: Comments sent by mail should be addressed to Meg Patulski, State Measures and Conformity Group, Transportation and Regional Programs Division, U.S. Environmental Protection Agency, 2000 Traverwood Drive, Ann Arbor, MI 48105.

Fax: Comments can also be faxed to the attention of Meg Patulski at (734) 214-4052.

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Meg Patulski, State Measures and Conformity Group, Transportation and Regional Programs Division, U.S. Environmental Protection Agency, 2000 Traverwood Drive, Ann Arbor, MI 48105, e-mail address:, telephone number: (734) 214-4842, fax number: (734) 214-4052.

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The contents of this notice are listed in the following outline:

I. What Is Transportation Conformity?

II. Background on the Draft Guidance

III. What Is in the Draft Guidance?

IV. Request for Comments

I. What Is Transportation Conformity?

Transportation conformity is required under Clean Air Act (CAA) section 176(c) (42 U.S.C. 7506(c)) to ensure that transportation plans, transportation improvement programs (TIPs) and federally supported highway and transit projects are consistent with (“conform to”) the purpose of the state air quality implementation plan (SIP). Conformity to the purpose of the SIP means that transportation activities will not cause or contribute to new air quality violations, worsen existing violations, or delay timely attainment of the relevant national ambient air quality standard(s) (NAAQS) or any interim milestones. Transportation conformity applies to areas that are designated nonattainment and those areas redesignated to attainment after 1990 (“maintenance areas”) for transportation-related criteria pollutants: Carbon monoxide (CO), ozone, nitrogen dioxide (NO2) and particulate matter (PM2.5 and PM10).[1]

EPA's transportation conformity rule (40 CFR Parts 51 and 93) establishes the criteria and procedures for determining whether transportation activities conform to the SIP. EPA first promulgated the transportation conformity rule on November 24, 1993 (58 FR 62188) and has subsequently published several amendments.

II. Background on the Draft Guidance

The conformity rule includes a specific requirement that certain transportation projects be analyzed for local air quality impacts (a “hot-spot” analysis), in addition to other conformity requirements. In its March 10, 2006 final rule (71 FR 12468), EPA stated that quantitative PM2.5 and PM10 hot-spot analyses would not be required until EPA releases hot-spot modeling guidance and an appropriate motor vehicle emissions model is available to conduct such hot-spot analyses.[2] For projects where a hot-spot analysis is required, the conformity rule requires a qualitative PM hot-spot analysis until EPA releases guidance on how to conduct quantitative PM hot-spot analyses and announces in the Federal Register that these requirements are in effect (40 CFR 93.123(b)). In addition, today's draft PM hot-spot modeling guidance is being released for public comment to comply with EPA's obligations under a settlement agreement.[3]

In keeping with the commitment EPA made in its March 2006 final rule (71 FR 12502), this draft guidance was developed in coordination with DOT (Federal Highway Administration and Federal Transit Administration) and with several transportation conformity stakeholder groups. In addition, EPA also worked with the California Air Resources Board (CARB) and the California Department of Transportation (Caltrans) to develop the portions of the guidance relating to the use of CARB's EMFAC2007 model in California.

III. What Is in the Draft Guidance?

The draft PM hot-spot modeling guidance describes conformity requirements for quantitative PM hot-spot analyses; provides technical guidance on estimating project emissions using EPA's MOVES2010 model, California's EMFAC2007 model, and other methods; and outlines how to apply air quality dispersion models for quantitative PM hot-spot analyses. The draft guidance also discusses how to calculate design values for comparison to each PM NAAQS, as well as how to determine which air quality modeling receptors may or may not be appropriate for PM hot-spot analyses.[4] The draft guidance also describes how the interagency consultation process should be used to develop quantitative hot-spot analyses in PM2.5 and PM10 nonattainment and maintenance areas. In addition, the draft guidance includes other resources and examples to assist in conducting quantitative PM hot-spot modeling analyses. However, the draft Start Printed Page 29538guidance does not change transportation conformity rule requirements for hot-spot analyses, such as what types of projects are subject to hot-spot analyses. EPA notes that the guidance, once finalized, would help implement existing requirements in the CAA and conformity rule and is not a regulation.

IV. Request for Comments

EPA is seeking comment on all aspects of the draft PM hot-spot modeling guidance. In particular, EPA is seeking comments on the following:

(1) Does the draft guidance provide sufficient information on how to configure and run MOVES2010 and EMFAC2007 at the project level?

(2) Do the air quality modeling sections of the draft guidance and references to other existing documents provide sufficient detail for air quality modelers to conduct PM hot-spot analyses using AERMOD or CAL3QHCR?

(3) Is there sufficient information in the draft guidance to calculate design values and determine appropriate receptors? If not, what additional information is necessary?

(4) Are there issues that the draft guidance does not address that should be addressed in the final guidance or in other EPA efforts?

(5) What types of outreach, training, and other technical assistance would be helpful in implementing the final guidance?

EPA encourages those submitting comments to provide specific details and/or examples wherever possible.

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Dated: May 17, 2010.

Margo Tsirigotis Oge,

Director, Office of Transportation and Air Quality.

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1.  40 CFR 93.102(b)(1) defines PM2.5 and PM10 as particles with an aerodynamic diameter less than or equal to a nominal 2.5 and 10 micrometers, respectively.

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2.  EPA's new motor vehicle emissions model, MOVES2010, was released in December 2009 and is capable of performing project-level emissions analyses from on-road sources. MOVES2010 will be approved for use in quantitative PM hot-spot analyses in areas outside of California when this draft guidance is finalized.

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3.  In May 2006, the Environmental Defense Fund, Natural Resources Defense Council, and Sierra Club challenged the March 2006 final rule (Environmental Defense et al. v. Environmental Protection Agency, No. 06-1164 (DC Cir.)). On May 19, 2007, petitioners and EPA entered into a settlement agreement in which EPA agreed to publish a Federal Register notice announcing the availability of the draft guidance for public comment for a period of at least 30 days.

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4.  EPA stated in the March 2006 final rule that the PM hot-spot modeling guidance would “consider how projects of air quality concern are predicted to impact air quality at existing and potential PM2.5 monitor locations which are appropriate to allow the comparison of predicted PM2.5 concentrations to the current PM2.5 standards, based on PM2.5 monitor siting requirements (40 CFR Part 58).” (71 FR 12471)

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[FR Doc. 2010-12607 Filed 5-25-10; 8:45 am]